Hello all. I have a 97,000 mile Excursion 4X4 V10 with 4.30's. All stock. The rear has the hum/vibration sound. I have done a lot of searching and found it is common, but need some guidance.
The ujoints were replaced last year by a Ford dealership at the prev owners request. I changed them out again as the pinion side (rear) had play. The slip yoke has some torsional play. I took it off and greased the splines. I have tried indexing the driveshaft, but it simply changes the type (speed) of vibration. I am down to either the shaft itself or the pinion bearings. What are the signs of bad bearings? I would think that if it was pinion bearings, indexing the driveshaft wouldnt change the vibration. The rear is full of grease and the fill plug had no noticeable metal other than the gray paste that is normal. I did check pinion angle. The rear has 2 degrees negative on the pinion and 7 degrees on the shaft. The transfer has 4 degrees negative. Any advice is appreciated.
Thanks.

 

Easiest way I've found to check for bad bearings is the wiggle test. Grab the yoke or DS and wiggle. The pinion bearing should be pretty solid and you should get next no deflection. An unbalanced DS should give you a little vibration in bottom of the seat, until the gears go, the pumpkin should just howl. I've also seen driveshafts smooth back out, typically at 20 to 30 mph faster than the speed the vibration started.

 

Is the vibration in the seat of your pants? If so I test DS or U-Joints by driving the vehicle at the speed the vibration is the worst, I then carefully put the vehicle in Nuetral and coast, If the vibration goes away its usually DS or U-Joints, I recently did this test on my brothers truck on Thanksgiving and sure enough his rear UJ was badly worn, so we replaced both and no more vibration. Remember when your under the truck checking for ware on driveline components you should have the vehicle in neutral so there is no torque on the driveline. Use a wheel chock for extra measure.

 

The vibration can be heard through the floor as a hum (my 8 year old asked why it sounded like a beehive in the third row seat). The pinion has no slop. You can feel the vibration through the gas pedal at it's worst. The ujoints are new and phased properly, but changing them made zero difference. If I twist the driveshaft at 180 degrees, the vibration changes. In that case, it starts at 58 mph and mellows out at 70 to the point you can change it by giving it gas and letting off. If the shaft is in it's original position, it is smooth until 70. It then hums no matter what you do until about 90 mph. The rear pinion has an obvious downward angle in relation to the driveshaft. My buddies F350 has the driveshaft directly pointed at the pinion. I may try some tapered blocks to mess with the pinion angle.
This is driving me CRAZY.

 

90 MPH in an excursion ???????

 

Also could be the bushing in tail shaft of the transfer case that centers the yoke before the U joint, if you can move that yoke up and down or side to side the bushing is bad, I had this problem on a 97 Expy after the U joint were bad and the vibration wore the bushing, my fault for letting it go too long

 

I wanted to see if the vibes stopped at any speed. I had no kids in the vehicle and it was a very empty stretch of interstate. As far as the tailshaft on the TC, it is tight. The only play at all in the rear driveline that I can find is the slip yoke and it is torsional.

 

I have a similar vibe that is noticable at 70 and increses with speed but I haven't tried 90. My drivers license is expired and I have some flags on my record due to a few old non running un-insured vehicles in the barn so i'm flying under the radar til I get it cleared up. I have a new drive shaft with all new joints. I replaced the shaft because it had a dent in it. The guy that made my shaft for me told me that if I had 3.70's instead of 4.30's I probably wouldn't have ever noticed it. I have noticed that if I load the back of my ex heavy enough to change the pinion angle slightly the vibe goes away. I think I am going to try some angle correcting shims. I have a set on some f-150 springs that came from the factory. This blocks on the f-150 are identical to the ones on the ex. It is odd to me that the 4x4 excursions have the lift blocks with no correction shims. Im gonna get him to re-balance the shaft if the shims dont fix it. The common thread seems to be 4x4 with 4.30 gears.

 

rukowh- I think we are going in the same direction. I seem to always buy vehicles that have either driveline vibes or tire vibes. Anyway, I have about 5 degrees negative pinion angle. The pinion is obviously down compared to the driveshaft. I am planning to add about two degrees or so using shims to see if it helps. My 03 F250 had the 2" blocks and I added the F350 4" blocks. After shimming the carrier bearing, the vibes it had went away. I just dont understand why they would not have corrected the angle from the factory on the X. The 4.30's change the shaft speed enough that it may make it vibrate. In my Mustang, I put the aluminum driveshaft to get rid of the vibes and it fixed it. That was with 3.55's. I then put in 4.56's and it developed a slight vibration at higher speeds. But, I wouldnt change the 4.30's for anything.

 

One other issue that I have that could cause the vibe is that I have a front hub that keeps sticking in the engaged position. Even when I'm in 2wd my front axles and shaft are spinning when it happens. I was considering changing to warn manual only hubs but then it rained twice last week and now I'm back on the autos. Have you checked your front driveshaft to see if it is turns free when the truck is in park?

 

My vibration issue is totally different. I feel a fairly heavy vibration from the rear end when pulling away from a stop and turning at the same time i.e. leaving a stop sign at the bottom of an off-ramp. I can also feel it while climbing the road into my neighborhood; a slow (15-20 mph) uphill left hand bend. No vibration at all on highway or any other situation.

I thought it was maybe a rear wheel bearing gone real bad but had them checked and shop said they were fine.

 

Some of the vibes might be worn tranny mounts letting the back of the tranfercase to move sum under different loads. or the socket in the cardan joint might be worn. Pinion angles are a big one also. Have you checked as to the runout, or staightness of the tube? and try pulling off the slip yoke and turning it 180 degrees and reinstalling it.

 

daves,
Get the t-case / shaft / pinion angles set correctly. Maybe the new springs and blocks changed the angles.

On a different vehicle, I had a set of lift springs that could install either end forward. One way sent the pinion down but the caster was good. The other way, vice-versa.
How do the V codes sit?

Sometimes... a d/s vibe does not show right away, the springs have to settle a bit, or some other wear lets it show. In that case the problem is not the normal wear & tear but the geometry was right on the line, then slipped into vibe mode.

Wasn't the angle was correct when it left the factory? And that's an honest question, not a comment.


I think the t-case and pinion need to be at equal & opposite angles. Google 'pinion angle' for more information.
Good luck

 

I recommend giving this company a call.. they know more about driveline vibrations that anyone... they can often identify a vibration just by description and vehicle speed range that it occurs . a buddy of mine used to work for them too.
Cannon Engineering Inc
(Drive Shafts By Cannon)
10921 Chandler Blvd, North Hollywood, CA 91601-2944

Contact Phone: (818) 508-0123
URL (web address):
Business Category: Mfg Motor Vehicle Parts/Accessories General Auto Repair in North Hollywood, CA
Industry (SIC): Motor Vehicle Parts and Accessories
Business Information

This company profile is for the private company Cannon Engineering Inc , located in North Hollywood, CA. Drive Shafts By Cannon's line of business is mfg motor vehicle parts/accessories general auto repair.
Company Name: Cannon Engineering Inc
Is This Your Company?
Address: 10921 Chandler Blvd, North Hollywood, CA 91601-2944 (Map)
Alt Business Name: Drive Shafts By Cannon
Location Type: Single Location
Est. Annual Sales: $1,000,000
Est. # of Employees: 10
Est. Empl. at Loc.: 10
Year Started: 1945
State of Incorp:
SIC #Code: 3714
Contact's Name: Donald Cannon
Contact's Title: President
NAICS: Motor Vehicle Transmission and Power Train Parts Manufacturing

 

Superfuzz, if you have a limited slip diff. you may need to add some friction modifier to you rear fluid. Better yet, if you have never changed the fluid out, replace it with Royal Purple rear diff fluid...it has the modifier already in it.